Critically ill patients with COVID-19-associated acute kidney injury treated with kidney replacement therapy: Comparison between the first and second pandemic waves in São Paulo, Brazil.

INTRODUCTION: This study aimed to compare the characteristics and outcomes of critically ill patients with COVID-19-associated acute kidney injury (AKI) who were treated with kidney replacement therapy (KRT) in the first and second waves of the pandemic in the megalopolis of Sao Paulo, Brazil. METHODS: A multicenter retrospective study was conducted in 10 intensive care units (ICUs). Patients aged ≥18 years, and treated with KRT due to COVID-19-associated AKI were included. We compared demographic, laboratory and clinical data, KRT parameters and patient outcomes in the first and second COVID-19 waves. RESULTS: We assessed 656 patients (327 in the first wave and 329 in the second one). Second-wave patients were admitted later (7.1±5.0 vs. 5.6±3.9 days after the onset of symptoms, p<0.001), were younger (61.4±13.7 vs. 63.8±13.6 years, p = 0.023), had a lower frequency of diabetes (37.1% vs. 47.1%, p = 0.009) and obesity (29.5% vs. 40.0%, p = 0.007), had a greater need for vasopressors (93.3% vs. 84.6%, p<0.001) and mechanical ventilation (95.7% vs. 87.8%, p<0.001), and had higher lethality (84.8% vs. 72.7%, p<0.001) than first-wave patients. KRT quality markers were independently associated with a reduction in the OR for death in both pandemic waves. CONCLUSIONS: In the Sao Paulo megalopolis, the lethality of critically ill patients with COVID-19-associated AKI treated with KRT was higher in the second wave of the pandemic, despite these patients being younger and having fewer comorbidities. Potential factors related to this poor outcome were difficulties in health care access, lack of intra-hospital resources, delay vaccination and virus variants.

Sodium glucose co-transporter-2 inhibitors in intensive care unit patients with type 2 diabetes: a pilot case control study.

BACKGROUND: Sodium glucose co-transporter-2 (SGLT2) inhibitors improve long-term cardiovascular and renal outcomes in individuals with type 2 diabetes. However, the safety of SGLT2 inhibitors in ICU patients with type 2 diabetes is uncertain. We aimed to perform a pilot study to assess the relationship between empagliflozin therapy and biochemical, and clinical outcomes in such patients. METHODS: We included 18 ICU patients with type 2 diabetes receiving empagliflozin (10 mg daily) and insulin to target glucose range of 10-14 mmol/l according to our liberal glucose control protocol for patients with diabetes (treatment group). Treatment group patients were matched on age, glycated hemoglobin A1c, and ICU duration with 72 ICU patients with type 2 diabetes exposed to the same target glucose range but who did not receive empagliflozin (control group). We compared changes in electrolyte and acid-base parameters, hypoglycemia, ketoacidosis, worsening kidney function, urine culture findings, and hospital mortality between the groups. RESULTS: Median (IQR) maximum increase in sodium and chloride levels were 3 (1-10) mmol/l and 3 (2-8) mmol/l in the control group and 9 (3-12) mmol/l and 8 (3-10) mmol/l in the treatment group (P = 0.045 for sodium, P = 0.059 for chloride). We observed no differences in strong ion difference, pH or base excess. Overall, 6% developed hypoglycemia in each group. No patient in the treatment group and one patient in the control group developed ketoacidosis. Worsening kidney function occurred in 18% and 29% of treatment and control group patients, respectively (P = 0.54). Urine cultures were positive in 22% of treatment group patients and 13% of control group patients (P = 0.28). Overall, 17% of treatment group patients and 19% of control group patients died in hospital (P = 0.79). CONCLUSIONS: In our pilot study of ICU patients with type 2 diabetes, empagliflozin therapy was associated with increases in sodium and chloride levels but was not significantly associated with acid-base changes, hypoglycemia, ketoacidosis, worsening kidney function, bacteriuria, or mortality.

Glycemic control and blood gas sampling frequency during continuous glucose monitoring in the intensive care unit: A before-and-after study.

BACKGROUND: Whether subcutaneous continuous glucose monitoring (CGM) can safely replace intermittent arterial blood gas glucose analyses in intensive care unit (ICU) patients remains uncertain. We aimed to compare CGM to blood gas glucose values and assess whether CGM use reduces blood gas sampling frequency and glucose variability in ICU patients with type 2 diabetes managed with liberal glucose control. METHODS: We used the FreeStyle Libre CGM in 15 ICU patients and compared their blood glucose metrics with a pre-CGM control population of 105 ICU patients with type 2 diabetes. Both groups received insulin to target glucose range of 10-14 mmol/L. We used linear regression analysis adjusted for illness severity to assess the association of CGM use with blood gas sampling frequency and glucose variability. We used mean absolute relative difference (MARD) and Clarke error grid analysis to assess accuracy of matched CGM-blood glucose values overall, across glucose stata (<10, 10-14, >14 mmol/L), and over time (≤48, 48-96, >96 h). RESULTS: We analyzed 483 matched glucose values. Overall MARD was 11.5 (95% CI, 10.7-12.3)% with 99% of readings in Clarke zones A and B. MARD was 15.5% for glucose values <10 mmol/L, 11.1% at 10-14 mmol/L, and 11.4% >14 mmol/L. MARD was 13.8% in the first 48 h, 10.9% at 48-96 h, and 8.9% beyond 96 h. CGM use was associated with 30% reduction in blood gas sampling frequency. CGM use was not associated with glucose variability as determined by glycemic lability index or standard deviation of blood glucose. CONCLUSIONS: In our cohort of ICU patients with type 2 diabetes receiving liberal glycemic control, CGM showed acceptable accuracy and was associated with a reduction in blood gas sampling frequency without compromising glucose control. Lowest accuracy was observed at glucose values below 10 mmol/L and during the first 48 h of CGM use.

Continuous bladder urinary oxygen tension as a new tool to monitor medullary oxygenation in the critically ill.

Acute kidney injury (AKI) is common in the critically ill. Inadequate renal medullary tissue oxygenation has been linked to its pathogenesis. Moreover, renal medullary tissue hypoxia can be detected before biochemical evidence of AKI in large mammalian models of critical illness. This justifies medullary hypoxia as a pathophysiological biomarker for early detection of impending AKI, thereby providing an opportunity to avert its evolution. Evidence from both animal and human studies supports the view that non-invasively measured bladder urinary oxygen tension (PuO2) can provide a reliable estimate of renal medullary tissue oxygen tension (tPO2), which can only be measured invasively. Furthermore, therapies that modify medullary tPO2 produce corresponding changes in bladder PuO2. Clinical studies have shown that bladder PuO2 correlates with cardiac output, and that it increases in response to elevated cardiopulmonary bypass (CPB) flow and mean arterial pressure. Clinical observational studies in patients undergoing cardiac surgery involving CPB have shown that bladder PuO2 has prognostic value for subsequent AKI. Thus, continuous bladder PuO2 holds promise as a new clinical tool for monitoring the adequacy of renal medullary oxygenation, with its implications for the recognition and prevention of medullary hypoxia and thus AKI.

Effects of changes in inspired oxygen fraction on urinary oxygen tension measurements.

BACKGROUND: Continuous measurement of urinary PO2 (PuO2) is being applied to indirectly monitor renal medullary PO2. However, when applied to critically ill patients with shock, its measurement may be affected by changes in FiO2 and PaO2 and potential associated O2 diffusion between urine and ureteric or bladder tissue. We aimed to investigate PuO2 measurements in septic shock patients with a fiberoptic luminescence optode inserted into the urinary catheter lumen in relation to episodes of FiO2 change. We also evaluated medullary and urinary oxygen tension values in Merino ewes at two different FiO2 levels. RESULTS: In 10 human patients, there were 32 FiO2 decreases and 31 increases in FiO2. Median pre-decrease FiO2 was 0.36 [0.30, 0.39] and median post-decrease FiO2 was 0.30 [0.23, 0.30], p = 0.006. PaO2 levels decreased from 83 mmHg [77, 94] to 72 [62, 80] mmHg, p = 0.009. However, PuO2 was 23.2 mmHg [20.5, 29.0] before and 24.2 mmHg [20.6, 26.3] after the intervention (p = 0.56). The median pre-increase FiO2 was 0.30 [0.21, 0.30] and median post-increase FiO2 was 0.35 [0.30, 0.40], p = 0.008. PaO2 levels increased from 64 mmHg [58, 72 mmHg] to 71 mmHg [70, 100], p = 0.04. However, PuO2 was 25.0 mmHg [IQR: 20.7, 26.8] before and 24.3 mmHg [IQR: 20.7, 26.3] after the intervention (p = 0.65). A mixed linear regression model showed a weak correlation between the variation in PaO2 and the variation in PuO2 values. In 9 Merino ewes, when comparing oxygen tension levels between FiO2 of 0.21 and 0.40, medullary values did not differ (25.1 ± 13.4 mmHg vs. 27.9 ± 15.4 mmHg, respectively, p = 0.6766) and this was similar to urinary oxygen values (27.1 ± 6.17 mmHg vs. 29.7 ± 4.41 mmHg, respectively, p = 0.3192). CONCLUSIONS: Changes in FiO2 and PaO2 within the context of usual care did not affect PuO2. Our findings were supported by experimental data and suggest that PuO2 can be used as biomarker of medullary oxygenation irrespective of FiO2.

Acute respiratory distress syndrome following administration of gadolinium contrast agent: a case report.

BACKGROUND: Gadolinium-based contrast agents are used extensively in magnetic resonance imaging to assist diagnosis of medical conditions. Despite their documented safety profile, severe adverse events do occur, and their documentation may serve to raise the awareness of the medical community. CASE PRESENTATION: We report the case of a 15-year-old white Latin American female patient admitted to the intensive care unit for acute respiratory distress syndrome following administration of gadolinium. She did not have rash or tongue swelling but developed hypotension responsive to fluid administration and severe hypoxemia. Chest computed tomography revealed bilateral pulmonary compromise with multiple confluent consolidations. She received methylprednisolone and noninvasive ventilatory support including bilevel positive airway pressure ventilation and high-flow nasal cannula, and underwent a rapid recovery. CONCLUSION: Gadolinium-based contrast agent-induced acute respiratory distress syndrome, albeit rare, should be included in the differential diagnosis of respiratory failure shortly after magnetic resonance imaging, which is nowadays a frequent diagnostic procedure, potentially increasing the awareness of this serious complication.

An algorithm to predict the need for invasive mechanical ventilation in hospitalized COVID-19 patients: the experience in Sao Paulo.

BACKGROUND: We aimed to characterize patients hospitalized for coronavirus disease 2019 (COVID-19) and identify predictors of invasive mechanical ventilation (IMV). METHODS: We performed a retrospective cohort study in patients with COVID-19 admitted to a private network in Sao Paulo, Brazil from March to October 2020. Patients were compared in three subgroups: non-intensive care unit (ICU) admission (group A), ICU admission without receiving IMV (group B) and IMV requirement (group C). We developed logistic regression algorithm to identify predictors of IMV. RESULTS: We analyzed 1,650 patients, the median age was 53 years (42-65) and 986 patients (59.8%) were male. The median duration from symptom onset to hospital admission was 7 days (5-9) and the main comorbidities were hypertension (42.4%), diabetes (24.2%) and obesity (15.8%). We found differences among subgroups in laboratory values obtained at hospital admission. The predictors of IMV (odds ratio and 95% confidence interval [CI]) were male (1.81 [1.11-2.94], P=0.018), age (1.03 [1.02-1.05], P<0.001), obesity (2.56 [1.57-4.15], P<0.001), duration from symptom onset to admission (0.91 [0.85-0.98], P=0.011), arterial oxygen saturation (0.95 [0.92- 0.99], P=0.012), C-reactive protein (1.005 [1.002-1.008], P<0.001), neutrophil-to-lymphocyte ratio (1.046 [1.005-1.089], P=0.029) and lactate dehydrogenase (1.005 [1.003-1.007], P<0.001). The area under the curve values were 0.860 (95% CI, 0.829-0.892) in the development cohort and 0.801 (95% CI, 0.733-0.870) in the validation cohort. CONCLUSIONS: Patients had distinct clinical and laboratory parameters early in hospital admission. Our prediction model may enable focused care in patients at high risk of IMV.

Characteristics and Risk Factors for Mortality in Critically Ill Patients with COVID-19 Receiving Invasive Mechanical Ventilation: The Experience of a Private Network in Sao Paulo, Brazil.

Introduction: The use of invasive mechanical ventilation (IMV) in COVID-19 represents in an incremental burden to healthcare systems. Aim of the study: We aimed to characterize patients hospitalized for COVID-19 who received IMV and identify risk factors for mortality in this population. Material and Methods: A retrospective cohort study including consecutive adult patients admitted to a private network in Brazil who received IMV from March to October, 2020. A bidirectional stepwise logistic regression analysis was used to determine the risk factors for mortality. Results: We included 215 patients, of which 96 died and 119 were discharged from ICU. The mean age was 62.7 ± 15.4 years and the most important comorbidities were hypertension (62.8%), obesity (50.7%) and diabetes (40%). Non-survivors had lower body mass index (BMI) (28.3 [25.5; 31.6] vs. 31.2 [28.3; 35], p<0.001, and a shorter duration from symptom onset to intubation (8.5 [6.0; 12] days vs. 10 [8.0; 12.5] days, p = 0.005). Multivariable regression analysis showed that the risk factors for mortality were age (OR: 1.07, 95% CI: 1.03 to 1.1, p < 0.001), creatinine level at the intubation date (OR: 3.28, 95% CI: 1.47 to 7.33, p = 0.004), BMI (OR: 0.91, 95% CI: 0.84 to 0.99, p = 0.033), lowest PF ratio within 48 hours post-intubation (OR: 0.988, 95% CI: 0.979 to 0.997, p = 0.011), barotrauma (OR: 5.18, 95% CI: 1.14 to 23.65, p = 0.034) and duration from symptom onset to intubation (OR: 0.76, 95% CI: 0.76 to 0.95, p = 0.006). Conclusion: In our retrospective cohort we identified the main risk factors for mortality in COVID-19 patients receiving IMV: age, creatinine at the day of intubation, BMI, lowest PF ratio 48-hours post-intubation, barotrauma and duration from symptom onset to intubation.

Urine biochemistry assessment in the sequential evaluation of renal function: Time to think outside the box.

Urine biochemistry (UB) remains a controversial tool in acute kidney injury (AKI) monitoring, being considered to be of limited value both in terms of AKI diagnosis and prognosis. However, many criticisms can be made to the studies that have established the so called "pre-renal paradigm" (used for decades as the essential physiological basis for UB assessment in AKI) as well as to more recent studies suggesting that UB has no utility in daily clinical practice. The aim of this article is to describe our hypothesis on how to interpret simple and widely recognized urine biochemical parameters from a novel perspective, propose the rationale for their sequential assessment and demonstrate their usefulness in AKI monitoring, especially in the critical care setting.

Concurrent hospitalization of a married couple presenting with distinct symptoms but diagnosed with a life-threatening infectious disease.

We described the cases of a married couple hospitalized for distinct symptoms and developed a neuroparalytic syndrome with rapid progression. In Case 1, a 75-year-old woman was admitted for abdominal pain, diarrhea, and blurred vision. The patient developed acute respiratory failure, ptosis, and ophthalmoplegia. She died on day 15 because of an acute abdomen. In Case 2, her husband, a 71-year-old man, was admitted for diplopia. The patient developed abdominal distension and slurred speech. Later, he developed bilateral ptosis, ophthalmoparesis, and mydriasis. Botulism was suspected, and both patients received botulinum antitoxin. Our male patient survived but underwent prolonged rehabilitation.

COVID-19-associated acute kidney injury patients treated with renal replacement therapy in the intensive care unit: A multicenter study in São Paulo, Brazil.

INTRODUCTION: Multicenter studies involving patients with acute kidney injury (AKI) associated with the disease caused by the new coronavirus (COVID-19) and treated with renal replacement therapy (RRT) in developing countries are scarce. The objectives of this study were to evaluate the demographic profile, clinical picture, risk factors for mortality, and outcomes of critically ill patients with AKI requiring dialysis (AKI-RRT) and with COVID-19 in the megalopolis of São Paulo, Brazil. METHODS: This multicenter, retrospective, observational study was conducted in the intensive care units of 13 public and private hospitals in the metropolitan region of the municipality of São Paulo. Patients hospitalized in an intensive care unit, aged ≥ 18 years, and treated with RRT due to COVID-19-associated AKI were included. RESULTS: The study group consisted of 375 patients (age 64.1 years, 68.8% male). Most (62.1%) had two or more comorbidities: 68.8%, arterial hypertension; 45.3%, diabetes; 36.3%, anemia; 30.9%, obesity; 18.7%, chronic kidney disease; 15.7%, coronary artery disease; 10.4%, heart failure; and 8.5%, chronic obstructive pulmonary disease. Death occurred in 72.5% of the study population (272 patients). Among the 103 survivors, 22.3% (23 patients) were discharged on RRT. In a multiple regression analysis, the independent factors associated with death were the number of organ dysfunctions at admission and RRT efficiency. CONCLUSION: AKI-RRT associated with COVID-19 occurred in patients with an elevated burden of comorbidities and was associated with high mortality (72.5%). The number of organ dysfunctions during hospitalization and RRT efficiency were independent factors associated with mortality. A meaningful portion of survivors was discharged while dependent on RRT (22.3%).

The hemodynamic effects of warm versus room-temperature crystalloid fluid bolus therapy in post-cardiac surgery patients.

INTRODUCTION: The contribution of fluid temperature to the effect of crystalloid fluid bolus therapy (FBT) in post-cardiac surgery patients is unknown. We evaluated the hemodynamic effects of FBT with fluid warmed to 40°C (warm FBT) versus room-temperature fluid. METHODS: In this single centre prospective before-and-after study, we evaluated the effects of 500 ml of warm versus room-temperature compound sodium lactate administered over <30 minutes, in 50 cardiac surgery patients admitted to ICU. We recorded hemodynamics continuous before and for 30 minutes after the first FBT. We defined CI responsiveness (CI-R) as an CI increase >15% of baseline immediately after FBT and effect dissipation if the CI returned to <5% of baseline and MAP responsiveness as >10% increase and dissipation as return to <3 mmHg of baseline. RESULTS: Hypotension (56%) and low CI (40%) typically triggered FBT. Temperature decreased >0.3°C in 13 (52%) patients after room-temperature FBT versus 0 (0%) after warm FBT (p < 0.01). CI and MAP responsiveness was similar (16 [64%] versus 11 [44%], p = 0.15 and 15 [60%] versus 17 [68%], p = 0.77, respectively). Among CI responders, CI increased more with room-temperature FBT (+0.6 [IQR, 0.5-1.1] versus +0.5 [IQR, 0.4-0.6] L/min/m2, p = 0.01). However, dissipation was more common after room-temperature versus warm FBT (9/16 [56%] versus 1/11 [9%], p = 0.02). CONCLUSION: In postoperative cardiac surgery patients, warm FBT preserved core temperature and induced smaller but more sustained CI increases among responders. Fluid temperature appears to impact both core temperature and the duration of CI response.

Concurrent hospitalization of a married couple presenting with distinct symptoms but diagnosed with a life-threatening infectious disease

ABSTRACT We described the cases of a married couple hospitalized for distinct symptoms and developed a neuroparalytic syndrome with rapid progression. In Case 1, a 75-year-old woman was admitted for abdominal pain, diarrhea, and blurred vision. The patient developed acute respiratory failure, ptosis, and ophthalmoplegia. She died on day 15 because of an acute abdomen. In Case 2, her husband, a 71-year-old man, was admitted for diplopia. The patient developed abdominal distension and slurred speech. Later, he developed bilateral ptosis, ophthalmoparesis, and mydriasis. Botulism was suspected, and both patients received botulinum antitoxin. Our male patient survived but underwent prolonged rehabilitation.

Comparison of the Hemodynamic and Temperature Effects of a 500-mL Bolus of 4% Albumin at Room Versus Body Temperature in Cardiac Surgery Patients.

OBJECTIVE: To compare the hemodynamic effect of room temperature (cold) 4% albumin fluid bolus therapy (FBT) with body temperature (warm) albumin FBT. DESIGN: Prospective, before-after trial. SETTING: A tertiary intensive care unit (ICU). PARTICIPANTS: Sixty ventilated, post-cardiac surgery patients prescribed with 4% albumin FBT. INTERVENTION: Cold or warm 4% albumin 500 ml FBT. MEASUREMENTS AND MAIN RESULTS: We recorded hemodynamic parameters before and for 30 minutes after FBT. Cardiac index (CI) and mean arterial pressure (MAP) responses were defined by a CI increase >15% and a MAP increase >10%, respectively. Immediately after FBT, median [interquartile range] core temperature changed by -0.3 [-0.4; -0.3] °C with cold albumin vs. 0.0 [0.0; 0.1]°C with warm albumin (P<0.001). The median CI increase was 0.3 [0.0; 0.5] L/min/m2 with 14 CI-responders (47%) in both groups (P>0.99). The median immediate MAP increase was 9 [3; 15] mmHg with cold albumin vs. 11 [5; 13] mmHg with warm albumin (P=0.79), with a MAP-response in 16 vs. 17 patients (P=0.99). There was an interaction between group and time for MAP (P=0.002), mean pulmonary artery pressure (PAP) (P=0.002) and core temperature (P<0.001). In the cold albumin group, after the initial response, MAP and mean PAP decreased more slowly than with warm albumin and, after the initial fall, core temperature increased toward baseline. CONCLUSION: In postoperative cardiac surgery patients, warm albumin FBT prevents the decrease in core temperature and, after an initial similar increase, is associated with a faster return of MAP and mean PAP toward baseline.

Accuracy of non-invasive body temperature measurement methods in critically ill patients: a prospective, bicentric, observational study.

Objective: The accuracy of different non-invasive body temperature measurement methods in intensive care unit (ICU) patients is uncertain. We aimed to study the accuracy of three commonly used methods. Design: Prospective observational study. Setting: ICUs of two tertiary Australian hospitals. Participants: Critically ill patients admitted to the ICU. Interventions: Invasive (intravascular and intra-urinary bladder catheter) and non-invasive (axillary chemical dot, tympanic infrared, and temporal scanner) body temperature measurements were taken at study inclusion and every 4 hours for the following 72 hours. Main outcome measures: Accuracy of non-invasive body temperature measurement methods was assessed by the Bland-Altman approach, accounting for repeated measurements and significant explanatory variables that were identified by regression analysis. Clinical adequacy was set at limits of agreement (LoA) of 1°C compared with core temperature. Results: We studied 50 consecutive critically ill patients who were mainly admitted to the ICU after cardiac surgery. From over 375 observations, invasive core temperature (mostly pulmonary artery catheter) ranged from 33.9°C to 39°C. On average, the LoA between invasive and non-invasive measurements methods were about 3°C. The temporal scanner showed the worst performance in estimating core temperature (bias, 0.66°C; LoA, -1.23°C, +2.55°C), followed by tympanic infrared (bias, 0.44°C; LoA, -1.73°C, +2.61°C) and axillary chemical dot methods (bias, 0.32°C; LoA, -1.64°C, +2.28°C). No methods achieved clinical adequacy even accounting for significant explanatory variables. Conclusions: The axillary chemical dot, tympanic infrared and temporal scanner methods are inaccurate measures of core temperature in ICU patients. These non-invasive methods appeared unreliable for use in ICU patients.

Accuracy of non-invasive body temperature measurement methods in adult patients admitted to the intensive care unit: a systematic review and meta-analysis.

Objective: Non-invasive thermometers are widely used in both clinical practice and trials to estimate core temperature. We aimed to investigate their accuracy and precision in patients admitted to the intensive care unit (ICU). Study design: Systematic review and meta-analysis. Data sources: We searched MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials to identify all relevant studies from 1966 to 2017. We selected published trials that reported the accuracy and precision of non-invasive peripheral thermometers (index test) in ICU patients compared with intravascular temperature measurement (reference test). The extracted data included the study design and setting, authors, study population, devices, and body temperature measurements. Methods: Two reviewers performed the initial search, selected studies, and extracted data. Study quality was assessed using the QUADAS-2 tool. Pooled estimates of the mean bias between index and reference tests and the standard deviation of mean bias were synthesised using DerSimonian and Laird random effects meta-analyses. Results: We included 13 cohort studies (632 patients, 105 375 measurements). Axillary, tympanic infrared and zero heat flux thermometers all underestimated intravascular temperature. Only oesophageal measurements showed clinically acceptable accuracy. We found an insufficient number of studies to assess precision for any technique. Study heterogeneity was high (99-100%). Risk of bias for the index test was unclear, mostly because of no device calibration or control for confounders. Conclusions: Compared with the gold standard of intravascular temperature measurement, non-invasive peripheral thermometers have low accuracy. This makes their clinical and trial-related use in ICU patients unreliable and potentially misleading.

Prolonged postoperative cerebral oxygen desaturation after cardiac surgery: A prospective observational study.

BACKGROUND: Near-infrared spectroscopy (NIRS) is used routinely to monitor cerebral tissue oxygen saturation (SctO2) during cardiopulmonary bypass (CPB) but is rarely employed outside the operating room. Previous studies indicate that patients are at risk of postoperative cerebral oxygen desaturation after cardiac surgery. OBJECTIVES: We aimed to assess perioperative and postoperative changes in NIRS-derived SctO2 in cardiac surgery patients. DESIGN: Prospective observational study. SETTING: The study was conducted in a tertiary referral university hospital in Australia from December 2017 to December 2018. PATIENTS: We studied 34 adult patients (70.6% men) undergoing cardiac surgery requiring CPB and a reference group of 36 patients undergoing non-cardiac surgical procedures under general anaesthesia. MAIN OUTCOME MEASURES: We measured SctO2 at baseline, during and after surgery, and then once daily until hospital discharge, for a maximum of 7 days. We used multivariate linear mixed-effects modelling to adjust for all relevant imbalances between the two groups. RESULTS: In the cardiac surgery group, SctO2 was 63.7% [95% confidence interval (CI), 62.0 to 65.5] at baseline and 61.0% (95% CI, 59.1 to 62.9, P = 0.01) on arrival in the ICU. From day 2 to day 7 after cardiac surgery, SctO2 progressively declined. At hospital discharge, SctO2 was significantly lower than baseline, at 53.5% (95% CI, 51.8 to 55.2, P < 0.001). In the reference group, postoperative SctO2 was not significantly different from baseline. On multivariable analysis, cardiac surgery, peripheral vascular disease and time since the operation were associated with greater cerebral desaturation, whereas higher haemoglobin concentrations were associated with slightly better cerebral oxygenation. CONCLUSION: After cardiac surgery on CPB, but not after non-cardiac surgery, most patients experience prolonged cerebral desaturation. Such postoperative desaturation remained unresolved 7 days after surgery. The underlying mechanisms and time to resolution of such cerebral desaturations require further investigation.

Continuous Magnesium Infusion to Prevent Atrial Fibrillation After Cardiac Surgery: A Sequential Matched Case-Controlled Pilot Study.

OBJECTIVE: The authors aimed to test whether a bolus of magnesium followed by continuous intravenous infusion might prevent the development of atrial fibrillation (AF) after cardiac surgery. DESIGN: Sequential, matched, case-controlled pilot study. SETTING: Tertiary university hospital. PARTICIPANTS: Matched cohort of 99 patients before and intervention cohort of 99 consecutive patients after the introduction of a continuous magnesium infusion protocol. INTERVENTIONS: The magnesium infusion protocol consisted of a 10 mmol loading dose of magnesium sulphate followed by a continuous infusion of 3 mmol/h over a maximum duration of 96 hours or until intensive care unit discharge. MEASUREMENTS AND MAIN RESULTS: The study groups were balanced except for a lower cardiac index in the intervention cohort. The mean duration of magnesium infusion was 27.93 hours (95% confidence interval [CI]: 24.10-31.76 hours). The intervention group had greater serum peak magnesium levels: 1.72 mmol/L ± 0.34 on day 1, 1.32 ± 0.36 on day 2 versus 1.01 ± 1.14 and 0.97 ± 0.13, respectively, in the control group (p < 0.01). Atrial fibrillation occurred in 25 patients (25.3%) in the intervention group and 40 patients (40.4%) in the control group (odds ratio 0.49, 95% CI, 0.27-0.92; p = 0.023). On a multivariate Cox proportional hazards model, the hazard ratio for the development of AF was significantly less in the intervention group (hazard ratio 0.45, 95% CI, 0.26-0.77; p = 0.004). CONCLUSION: The magnesium delivery strategy was associated with a decreased incidence of postoperative AF in cardiac surgery patients. These findings provide a rationale and preliminary data for the design of future randomized controlled trials.